Charles e



(No Model C. SCRIBNER. ELEGTROMAGNBT.

UNITED STATES PATENT OFFICE.

CHARLES E. SCRIBNER, OF CHICAGO, ILLINOIS, ASSIGNOR. TO THE IVESTERN ELECTRIC COMPANY, OF SAME PLACE.

ELECTROIVIAGNET..

SPECIFICATION forming part of Letters Patent No. 584,416, dated June l5, 1897'.

Application filed November 4, 1895. Serial No. 567,837. (No model.)

Tn n/,ZZ whom t may concern.-

Be it known that I, CHARLES E. SCRIBNER, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Electromagnets, (Case No. 405,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.`

My invention concerns, broadly, the construction of electromagnets, its aim being to produce an electromagnet which shall respond to alternating or pulsating electric currents, but which shall remain inert when traversed by undulating or continuous currents.

The immediate object of the invention is to provide a polarized signal-bell for telephonelincs which shall remain undisturbed by current continuously iiowing through it, but shall be sensitive to alternating signaling-currents.

The essential novelty of my invention consists in the combination, with an electromagnet and its armature, of a bridge or magnetic shunt of magnetic material between the poles of the electromagnet and a magnetizin'g-helix upon the bridge, adapted to nullify the polarity of the magnet-poles, or, in otlier words, tocreate a condition of no differeiice of magnetic potential between the poles. The armature is by this device perfectly shunted by the bridge while continuous currents traverse the magnet-helices.V For the purpose of malring the magnet responsive to alternating currents this bridge is surrounded by a closed conducting-circuit, as by a tube of copper, by which rapid i'luctuations of the induction in the bridge are obstructed, so that when the magnet-coils are traversed by rapidlyvarying currents the null condition of the magnet-poles is not attained, and the poles act upon the armature in the usual way to effeet its movement. In utilizing this contrivance in a polarized electric bell a constant polarity is imparted to the electromagnet by means of a permanent magnet in proper relation to it. The armature is centrally pivoted in the manner shown in Patent No. 210,886, dated December 17, 1878, to T. A. lVatson, and carries a tongue oscillating between gongs. A bell thus organized will remain unaffected when traversed by an unvarying or constant current of any strength, but will respond to Iluctuations or alternations in the current through it, such as are produced by the action of a generator of sig- Daling-current, with an ciiiciency substantially as great as that ofthe ordinary polarized signal-bell. l

The invention is shown in the accompany- 6o ing drawings.

Figure l of the drawings represents the elements of the electromagnet in a diagrammatic manner. Fig. 2 is a front elevation of the polarized signal-bell. Fig. is a section of a portion oi' the bell through the magnetic bridge and its surrounding tube and magnetizing-helix. Fig. t is a side elevation ol' the bell. Fig. 5 is a diagram illustrating thc use of the bell in a telephone-line in which a cur- 7o rent circulates constantly for the purpose of charging a storage battery at the substation.

The essential and novel features of the invention may be described with reference to Fig. l.

The usual U-shaped core a of the electromagnet is provided with a bridge a integral with it, the pole-pieces a2 a3 projecting beyond the bridge and being presented to the armature Z). Upon the bridge a is placed a 8o closed conducting-circuit c, represented as a short-circuited coil of low resistance, which may in practice be a tube of non-magnetic metal. Heliees d and d are wound upon two limbs of the core ai, and a third helix (Z2 is 85 wound upon the bridge a outside the coil or winding c. Coils d, d2, and d are connected in series. The coils d and d' may be. of the usual size and resistance-say of one thousan dl ohms. Coil d2 may be of any suitable resist- 9o ance, but should have a magnetizing effect with relation to coils d and d' such that it may produce in the bridge a an induction equal to that produced by coils d and d in the core a, and in the same direction in 95 the circuit. Under this condition when the three helices are traversed by a steady current there will be a condition of no dii'ierence of magnetic potential between the extremities of the bridge a', or, in other words, 10o

this bridge will be a perl'ect short circuit ol' the magnet and will prevent the magnetizing of pole-pieces a2 and fr". The armature b will therefore not be attracted. lVhen, however, the current through these helices is caused to vary quickly, corresponding iluctuatiens of the induction through the bridge a' are obstructed or largely prevented by the currents induced in the shortcircuited coil or tube c in a manner well known. The shortcircuited conductor c thus both directly impairs the etliciency oi the bridge a as a magnetic shunt and shields this bridge from the action of the helix d2, the effect being substantially equivalent to the removal or interruption of the bridge a' during the passage ot the varying current. Hence the armature l) is attracted and brought into motion when the magnet is traversed by alternating or other rapidly-varying currents.

The magnetic bridge surrounded by the closed conducting-cireuit (the copper tube) is of course alone efifective to a certain extent in reducing the dilierenee of magnetic potential at the poles when the magnet is excited by continuous currents. Hence the bell is operative in a degree when the winding d? is omitted. The best el'lec is, however, obtained with the complete device as described.

Figs. 2, 3, and t illustrate the application of this contrivanee in a polarized electric bell of well-known type. The electromagnet is carried in a frame, at one extremity et which, opposite the pole-pieces a2 ai of the magnet, the armature l) is carried by trunnions at its center. The same frame carries upon posts a pair of gongs c, between which oseillates a hammer f, carried by a tongue j", secured to the armature l). A bent permanent magnet g has one extremity tixed to the yoke of the electromagnet and the other presented to the armature ZJ, so that the latter is permanently magnetized by induction with like poles at its extremities. The bridge a maybe a small bar of iron let into the pole-pieces a2 a3. It is surrounded by a cylinder or tube c of copper, which is provided with flanges or heads near its extremities, the space between the heads being 'filled by the coil (l2. W'hile a steady current is flowing through the coils ot this bell the electromagnet exerts no attraction upon its armature l), and since the latter is lnagnetized by permanent magnet g with consequent poles at its center it lies indiften ently at either side. "When, however, an alternating signaling current linds circuit through the bell, the magnetic bridge and the coil cl2 cease to perform their function, the pole-pieces are alternately magnetized in opposite directions through the agency et helices (l and cl', and the armature is thrown into vibration. Obviously if the si gnaling-curn rent were not actually reversed, but only raised above and depressed below a certain average or normal value, the ellect upon the essere armature would be the saine as that produced by an alternating current.

In telephone-exchange practice it has seinetinies been found desirable to provide at the substation of a line a storage battery l`or operating the station-transmitter, the battery being' charged by a current constantly llowing in the line lroln a central source, but it has been found that such steadily-[lowing current interfered with the operation ot the ordinary type et polarized bell. Fig. 5 represents such an organization ot' circuits, including my improved bell at the substation.

Telephone-line l 2 extends from a substation 7i to a central station t. At the substation the circuit includes serially a storage battery 7D' of two cells and three windings d, d', and cl2 of the bell Y. At the central station the line includes an ann unciator in and an impedance-coil n and is led to the terminals of the central charging-battery o. The line is connected with the usual spring-jack p. A plug (l is represented, which, when introduced into spring-jack p, serves to connect a source r of alternating sign alin g-currentin a bridge of the line-circuit l 2 at the exchange, the continuity of this circuit being controlled, however, by the usual. ringing-key S.

The circulation of the charging -current in the line leaves the bell Z normally inert. Then the source r of signaling-current is connected with the line,tluetuations are produced in the line-circuit l 2 which ei't'ect the opcration et the bell. lil the source r et signalingcurrent be et sufficient strength with relation to battery o, it may create an alternating current in the line-circuit, but il the electrometive force of the source of signaling-current be less than that of battery o clearly the resulting sign alin g-eurrent would be onlya pulsating or undulating current. in either case the bell may be efficiently actuated without disconnecting the battery o.

claim as new and desire to secure by Letters Patentl. The combination with an electromagnet, of a bridge of magnetic material between its poles, a coil encircling the bridge, and means for producing current in the coil, said coil be- IOO IIO

ing adapted to create a condition of no dil'ference ot magnetic potential between the poles of the magnet, substantially as described.

2. The combination with an electromagnet, of a bridge et magnetic material uniting its poles, a closed conductingcircuit and a coil encircling the bridge, and a source of current in circuit with said coil, the coilbeing adapted to produce a condition of no difference of magnetic potential between the magnet-poles, as described.

3. The combination in an electromagnet, of a core terminating in pole-pieces, windings on the core, a bridge oi' magnetic material uniting the polepieces, a closed conductingeircuit and a winding encircling the said bridge, all ol said windings being' connected in the same electrical circuit, the lastmentioned winding being adapted -to neutralize the effect of the other two windings upon the pole-pieces, substantially as described.

4. In an electric bell the combination with the electromagnet and the centrally-pivoted polarized armature thereof, of a bridge of magnetic material uniting the poles ot' the magnet, and a closed conducting-circuit encircling the bridge, as described.

5. The combination in an electric bell, of the electromagnet and the centrally-pivoted polarized armature thereof, a bridge of magnetic material uniting the poles of the electromagnet, a closed cond acting-circuit and a winding encircling` the said bridge, the said winding being in a circuit with the windings of the electromagnet and being adapted to neutralize the effect of the said magnet-win d- CHARLES E. SCRIBNER.

lYitnesses:

ELLA EDLER, LUCILE RUSSELL. 

